The invention relates to a covering composition, a method and a device for isolating tooth material to be treated and producing a shield for the surrounding gums and/or adjacent teeth.
With some dental treatments, aggressive chemical substances are used in the mouth which can cause burning to the oral mucosa. Amongst these is the acid etching technique at the dental surgery, in the context of applying a composite filling and bleaching with preparations containing a high percentage of peroxide (in-office bleaching). With the acid etching technique the dental enamel is treated with a highly-concentrated, usually approximately 35 wt. % phosphoric acid within a prepared tooth cavity to improve the adhesion before the application of a primer and/or bonding. The phosphoric acid solution or phosphoric acid gel is then left to act for approximately 30 seconds on the dental enamel. In particular with preparations whose edges lie in the vicinity of the gum or an adjacent tooth, it is necessary for this tissue to be shielded from the etching means. It is further desirable to protect the treated tooth, or similarly a plurality of teeth, relative to the surrounding tissue of the oral cavity in a leak-tight fashion, to prevent, for example blood or saliva from reaching the treated tooth.
With the ‘in-office’ bleaching treatment, bleaching agents with a content of up to 35 wt. % hydrogen peroxide are directly applied onto the surface of the tooth to whiten the teeth. In particular when whitening vital teeth the bleaching agent is applied on the external surfaces of the tooth up to the vicinity of the gum margin. A protective cover of the oral mucosa is also imperative in this case to prevent burning.
A possibility for shielding consists in the use of a resilient sheet made from rubber which is referred to as a dental dam. The dentist then has to perforate the sheet at suitable points and punch out holes of a corresponding size in the sheet, through which the teeth to be treated are subsequently pushed. Where the size of the holes is unsuitable or where there are imperfections on the surface of the tooth, the problem frequently arises that the resilient sheet does not sit and seal precisely or tightly enough along the gum margin and thus does not sufficiently protect the oral mucosa. The positioning of a dental dam is regarded by many dentists as too costly and awkward. The danger arises that when stretched or during the treatment the rubber tears or loosens. As a result the isolating effect of the dental dam is lost and the material present on the exterior of the rubber sheet can enter the oral cavity. Patients find the cumbersome equipment and the fastening of the rubber on the neck of the tooth unpleasant.
In U.S. Pat. No. 6,305,936 compositions and methods are cited which are designed to overcome the above-mentioned disadvantages of the dental dam technique when sealing soft tissue parts in the mouth interior. A polymerisable material is protected in the Patent which comprises at least one monomer, a curing agent and at least one further compound. The compositions are conventional, light-curing acrylate systems which have to be considerably modified for use on soft tissues. As free-radical polymerisation of acrylates initiated by light releases a large amount of heat during cross-linking, when this system is used on oral soft tissue, such as for example the gums, a non-reactive additive such as mineral oil or polyol must be added to the mixture to ensure that the tissue of the patient does not suffer any burns. The addition of a plasticiser is therefore also necessary to reduce the cross-link density of the acrylate and thus to be able to ensure that the polymerised material can be removed again from the tissue after the treatment. By adding a reflective material, such as for example mica, a portion of the energy radiated by the polymerisation lamp into the mixture is intended to be reflected, thus to help reduce the resulting heat energy in the mixture.
Furthermore, the addition of a thickening agent to the polymerisable composition, such as for example xanthan gum, cellulose derivative, carboxypolymethylene, polyethylene oxide or high molecular weight polypropylene glycol is recommended in the Patent to provide it with muco-adhesive properties.
It can be seen that only by modifying the acrylate system at extremely high cost can a formulation be produced which corresponds to the most approximate criteria for the use of the formulation on soft tissues. A particular disadvantage of the invention moreover is that by using a plasticiser an attempt is made to reduce substantially the degree of polymerisation. A reduced degree of polymerisation allows the presence of either free monomers or corresponding oligomer structures of lower molecular weight. It is known that polymer compounds with a molecular weight of less than 1000 g/mol easily pass through biological membranes and bioaccumulate. (J H Hamilton, R Sutcliffe, Ecological Assessment of Polymers, 1996, Page 274). In the case of the very toxic acrylate components bis-GMA or HEMA, a reduced degree of polymerisation might consequently lead to cytotoxic problems when the invention is used. A further disadvantage is the time-consuming use of irradiation with a polymerisation lamp. As a result, depending on the width of the light outlet window, each piece has to be polymerised for 20 seconds, piece by piece.
The object of the present invention is therefore to provide a covering composition, a method and a device for isolating a tooth material to be treated and producing a shield for the surrounding gums and/or adjacent teeth from dental treatments which, relative to the prior art, can be more rapidly applied and are more comfortable and less toxic to use.